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Amateur Radio Data Transmissions - For discussion of all modes used to send data such as APRS and packet.

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Old 12-29-2016, 3:07 PM
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Question I need help with APRS

Hello! I am new to APRS and so far I'm hooked! I love it! But there are a bunch of things I want to do. First and most important is I am launching a high altitude balloon and I am equipping it with an APRS tracker. My problem is when I am looking for the payload on the ground I would like to decode the packets from it considering there probably will not be any digipeters or igates where it will land an I do not want to walk around the forest with a laptop in one hand and my HT in my other so I want to be able to connect it to my phone and decode packets that way. I built a cable for my UV-5R that allows me to use APRSDroid which works well except it only allows me to send my location and use it as a tracker and not a decoder. Is there a way to accomplish that from my phone. (keep this cheap I'm on a budget) Also I set up an igate using an RTL-SDR, SDR# and APRSIS32, first I hate having SDR sharp open just so I can send the audio to the packet engine and then to APRSIS32. Is there a more efficient way? Also I don't fully know how to use APRSIS32 and would also like to make a more efficient system like with a Raspberry Pi (but I cannot see the traffic with that system) And last but not least if I hook up my Mobile rig I keep in my house to a TNC and then to my computer (being able to Xmit as well as receive) does that give me any benefits if i can transmit for example have an igate and a digipeter or is that useless?

Thanks!
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Old 12-29-2016, 8:41 PM
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With regard to high altitude balloon APRS packages, make sure you use a GPS receiver that will work at high altitude. Some GPS receivers become unreliable above about 35,000 feet. Also, please do not use an APRS path that asks for any hops when you are at altitude. If your balloon is at 5,000 feet and you ask for the normal 1 or 2 hops, you are going to light up many digipeaters with your 5,000 foot antenna. Each of those hops tends to clog the APRS network. There are some APRS packages, such as the ones from Argent Data, that have switchable profiles so you can set one profile to beacon with "normal" settings below let's say 2,000 feet and another profile that beacons with no hops above that altitude.

I don't have any experience using APRSdroid to send packets using a connected radio, but I have heard that it's possible. You may need to do a little Googling on that one.

I'm not aware of any way to get from an SDR to APRSIS/32 without using some piece of software to decode what the SDR is hearing into audio which can then be converted into serial data using something like AGWPE. I would just eliminate the SDR and use an inexpensive radio.

One solution is to get an APRS radio such as a Kenwood TH-D72. It has an internal GPS receiver, internal TNC, and the firmware to decode APRS packets. One of the screens in the D72 will show you the distance and bearing to a received APRS packet.

I-gates and digipeaters are not the same thing. Digipeaters help extend the range of your APRS station by repeating your transmitted packets. I-gates send received APRS packets to the APRS-IS so they can be seen by Internet apps. What exactly do you want to do with your home station?
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Old 12-29-2016, 8:50 PM
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For the tracker I am using a pre-built device for that purpose called the TrackSoar so it should work fine at high altitudes. Also I don't know what a hop is so I'm not sure what you are talking about. I will try to use an inexpensive radio instead with a USB sound card. For my home station I want to have an igate I think I will leave it at that. As for receiving packets from the tracker I don't want to buy a radio like that because they are quite expensive and I am on a budget.

Thanks!
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Old 12-29-2016, 9:25 PM
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Quote:
Originally Posted by W9BU View Post
...I'm not aware of any way to get from an SDR to APRSIS/32 without using some piece of software to decode what the SDR is hearing into audio which can then be converted into serial data using something like AGWPE. I would just eliminate the SDR and use an inexpensive radio.
...
I *decode* APRS all the time using just an SDR (a dongle will do), no audio cables, and no serial data. I usually use HDSDR for the front end (use the .dll for the cheap dongles, or the ones freely available for AirSpy and the one for SDRPlay). Put it in wide FM mode, adjust the filter by pulling in the right slide of the lower right plot in the display and by using the slider. Install the free program VB Cable (virtual cable). Set it for 192 kHz (or lower there is no need as you are not going to be using your PC audio), set HDSDR for output to VB Cable input instead of speakers. Now set your packet decoder program for VB Cable instead of microphone input. Works fine and you can use this to copy packet/APRS using just a dongle, an antenna, and no cable. No dealing with serial data, audio cables or anything like that. I cannot though comment on it being formatted by whatever programming for whatever you intend to do. Serial cables and audio cables are fast going out of the way as a good way to do things. In summary, a PC, free software, a USB dongle, and antenna will decode APRS with no other cables, or complications without using any additional PC ports including the PC audio.

Using audio cables or converting to serial and then having to deal with serial-to-USB issues to decode packet is just silly today. Now if you want to transmit, things have not yet caught up for that.
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Old 12-30-2016, 8:44 AM
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I'm going to ask a question I should have asked from the outset: Do you have your amateur radio license?

Quote:
Originally Posted by gregory21greg View Post
For the tracker I am using a pre-built device for that purpose called the TrackSoar so it should work fine at high altitudes.
The TrackSoar transmitter is only rated for 300 mW. That might work OK while aloft, but once it's on the ground, especially in rough terrain, it may be a little difficult to find.

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Originally Posted by gregory21greg View Post
Also I don't know what a hop is so I'm not sure what you are talking about.
APRS transmitters send out beacons with the station callsign, location, and other data. Part of that beacon is an APRS path which uses aliased callsigns to request how the packet is to be digipeated. For example, if the path in your APRS beacon is "WIDE1-1", every digipeater configured to act on WIDE1 paths will look at the number of hops requested, the "-1" part of the path, and they will digipeat your beacon. When they digipeat your beacon, they will decrement the hop request from "-1" to just blank. When any other digipeater hears your digipeated beacon, it will see that the hop request is blank, so it will just ignore your packet. Typically, mobile APRS stations use a path of "WIDE1-1,WIDE2-1". This means your packet will be digipeated by either WIDE1 or WIDE2 digipeaters and you will get no more than 2 hops.

For a vehicle driving around with an APRS tracker, it's antenna is probably no more than 10 feet above ground, so it's foot print is fairly small. Depending on how many digipeaters are in the area, not very many will hear the vehicle's beacon because of the low profile antenna. In most parts of the country, the APRS network has been built with the understanding that the beacons are coming from a low altitude. So, if you send a "WIDE1-1,WIDE2-1" beacon from your vehicle, maybe one digipeater hears it, digipeats it and maybe one more digipeater hears the digipeated beacon. As a result, your beacon doesn't go very far which is the whole purpose of APRS (local, tactical information). Now, put your APRS tracker in a high-altitude balloon. Because your antenna is now at a great height, many more digipeaters hear your beacon. If you are still asking for a "WIDE1-1,WIDE2-1" path, your one beacon is going to light up digipeaters over a very wide area. This floods the network with your beacons and isn't very friendly to the other APRS users. Remember, the APRS network is a shared network and we all have to get along.

Quote:
Originally Posted by gregory21greg View Post
For my home station I want to have an igate I think I will leave it at that.
Why do you think you need an I-Gate at your home station? Are there no other I-Gates in your area?
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Last edited by W9BU; 12-30-2016 at 8:53 AM..
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Old 12-30-2016, 11:02 AM
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Heres an website to check out APRS: Automatic Packet Reporting System so you can learn more on aprs....
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Old 12-30-2016, 3:43 PM
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Of course I have my amateur radio licence KM6FRE is my call. The 300mw is not a problem I have that all figured out. OK I will make sure to not flood the system for the courtesy of others thank you for telling me that other wise I probably would have without realizing.I live on the foot of a mountain so I get horrible reception when experimenting with APRS so I made my own igate to solve that problem. Also it just fun to see the trafic. I will take a look at that link thank you.
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Old 12-30-2016, 5:36 PM
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You might be able to track the baloon using the Google Maps APRS web site. Type in the SSID in the top right text box.

At altitude, it will be heard by many iGates and should be easy to follow, but near the ground, you may lose it.

We have a couple of high schools that do high altitude balloon launches. I use aprs.fi to follow the balloon to its maximum altitude and then see the chase cars close in on it when it's back on the ground waiting to be recovered.

If you have a smart phone or tablet, you can track using them too as long as you have some sort of mobile data plan..
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Old 12-30-2016, 6:28 PM
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Buy a used Kenwood THD7 or other radio that has APRS support built into it. It will tell you right on the screen "Your balloon is ## miles that-a-way" and it will have way better sensitivity than any BaoFeng product.
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Old 04-13-2017, 12:56 PM
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If you have the audio levels right, APRSdroid will try to decode packets. The software decoder isn't as good as a hardware one, but if you've got a clean signal at the right levels, it'll work. It's easy to overdrive the mic input, though, especially if you forgot a DC Blocking capacitor in your cable. You may also need a resistive divider to lower the signal level to what your phone expects.
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Old 04-13-2017, 3:37 PM
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I have to agree with a Kenwood or Yaesu hand held with APRS included. They are so much easier to use. KISS.
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Old 04-22-2017, 8:48 AM
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Default APRSDROID can track and find other stations on your phone

I use APRSDROID software on my phone to do exactly what you want. I have an Aprs transmitter in my car and use Aprsdroid software on my Android phone with a cheap HT and a tiny "Mobilink" device (Welcome to mobilink.com) to find my car when hiking and exploring in the desert or the mountains. I have an off line map downloaded into the phone so that no cell signal is needed to see the car (or any other Aprs station I have received) on the phone display and the distance to it. I think that you can wire the radio audio into your phone and skip the "Mobilink" if all you need to do is track/find something and not transmit your own location.

Any Aprs packet that is received by Aprsdroid on your phone has it's call sign displayed on the phone. If you you tap that call sign, you can see it's location and distance from you on the off line map on the phone. I usually park my vehicle in a canyon or valley so it is not visible to others when hiking, and have used this set up to find my car. I also fly an Ultralight plane and several of us have our ham license and use this method to track each other when flying, and to find someone who has an "engine out" in the desert.

Good luck
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Old 04-22-2017, 9:32 AM
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Quote:
Originally Posted by Leelorr View Post
tiny "Mobilink" device (Welcome to mobilink.com)
I think this is the correct URL
Mobilinkd | Highly mobile packet radio
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